Asset tracking for the purposes of inventory control or the like is employed in a multitude of industry sectors such as in the food industry, apparel markets and any number of manufacturing sectors, to name a few. In many instances, a bar coded tag or radio frequency identification (RFID) tag is affixed to the asset and a reader interrogates the item to read the tag and ultimately to account for the asset being tracked. Although not readily adopted, an analogous system may be employed in a medical environment to track equipment such as an Electrocardiogram (EKG) machine or other modular patient monitoring equipment.
Of particular note is a surgical environment in which for preparation of surgery a previously sterilized instrument kit of surgical instruments and disposable items (collectively referred to as surgical items) is brought into a surgical suite. The instrument kit contains an assortment of surgical items including hemostats, clamps, forceps, scissors, sponges, and the like, based on the type of surgery to be performed. Typically, a scrub nurse removes the surgical items from the kit and arranges them on a back table located behind the operating table. The surgical items are organized in rows on rolled toweling for ease of access and handling by a surgeon and supporting team. During the course of a surgical procedure, the surgical items are often positioned on a “Mayo” stand proximate the operating table, while the unused surgical items remain on the back table. During the course of and at the conclusion of the surgery, all of the surgical items must be carefully counted to, among other things, avoid leaving any surgical items in a patient.
In view of the consequences, surgical items are typically counted at least three times during the course of a surgical procedure. The first count is performed prior to the start of the procedure; the second count is performed prior to a closure of the patient; the third count is performed at the conclusion of the procedure. In many instances such as when more than one surgical team is assigned to a procedure, many more counts of the surgical items, often involving different personnel (e.g., a circulating nurse and a scrub nurse), are performed. As a matter of fact, the Association of PeriOperative Registered Nurses (AORN) advocates four counts of the surgical items as part of its recommended practices for surgical procedures. Additionally, to keep track of the counts of the surgical items, rudimentary systems such as visual records scribbled on whiteboards or other more progressive computer tallying systems to designate the count of the surgical items are often employed.
In common practice, access to and from an operating room in the surgical suite is restricted during the counting process thereby resulting in a detention of valuable professional personnel. A discrepancy in the count must be resolved by additional counts, physical examination of the patient or x-ray examination, if necessary. Although it is unusual for a discrepancy in the count to result from a surgical item remaining in the patient, counting and recounting occurs in every surgical procedure and the repercussions associated with the loss of a surgical item is of grave concern to a medical facility and the medical professionals.
Thus, the multiple manual counting of surgical items is time consuming, ties up key professional personnel, contributes to surgical suite down time, distracts personnel from the surgical procedure, lengthens the time the patient is exposed to anesthesia leading to an increase in mortality and morbidity risk, is generally distasteful to all involved, and still results in errors wherein materials are left in the patient. It should be quite understandable that the average cost overruns of such delays associated with the personnel, capital equipment and the surgical suite itself can run into the tens of thousands of dollars per procedure. On an annual basis, the loss of productivity associated with the surgical suite is quite sizeable and should be addressed to bolster the bottom line of a medical facility.
Even with the degree of caution cited above, the problem associated with the loss of surgical items, especially surgical items retained within patients, is a serious one and has a significant influence on the costs of malpractice insurance. As a matter of fact, retained foreign bodies within a patient is one of the most prevalent categories of malpractice claims and the most common retained foreign body is a sponge. In accordance therewith, there is a diagnosis known as “gossypiboma” (wherein gossypium is Latin for cotton and boma is Swahili for place of concealment) for the retention of a sponge-like foreign body in a patient. The medical literature is scattered with reports of presentations of retained sponges found days, months, or even years after a surgical procedure.
The sponge is typically made of gauze-like material with dimensions often covering a four-inch square or a two-inch by four-inch rectangle. At one time sponges were commonly made of cotton, but now a number of filament materials are used. Occasionally, a filament of radiopaque material [e.g., barium sulfate (BaSO4)] is woven into the surgical sponge. The filament is provided to produce a distinct signature on an x-ray machine for the purpose of determining if a sponge is present in the patient. While this is generally effective, even these filaments are not 100% effective in aiding the location of the sponges. Different researchers report that x-ray methods to supplement manual counting are fallible.
Moreover, in cases when a sponge remains in the body for a long time, the radiopaque filament can become difficult to locate and may even conform to internal structures. Some have suggested that a computerized tomography (CT) scan can be more effective than an x-ray examination because the CT scans and ultrasonography may detect the reduced density of a sponge and its characteristic pattern of air bubbles trapped within the sponge. Many radiologists have published a number of papers over the years on the problem of finding lost sponges and these are generally known in the field of medicine.
As mentioned above, there is a widespread practice in other fields for counting, tracking and accounting for items and two of the more prevalent and lowest cost approaches involve various types of bar coding and RFID techniques. As with bar coding, the RFID techniques are primarily used for automatic data capture and, to date, the technologies are generally not compatible with the counting of surgical items. A reason for the incompatibility in the medical environment for the bar coding and RFID techniques is a prerequisite to identify items covered in fluids or waste, and the exigencies associated with the sterilization of surgical items including a readable tag.
Outside of the surgical suite, the medical community is not unfamiliar with various forms of automatic identification, counting, and accounting systems and methods. For example, U.S. Pat. No. 4,164,320, entitled “Patient and Specimen Identification Means and System Employing Same,” to Irazoqui, et al., describes a magnetic encoding technique for positive identification of patients and specimens associated with a particular patient. For the most part, Irazoqui, et al. and other references primarily use machine-readable technologies such as bar coding and magnetic stripes. The medical community in general recognizes that automatic identification, counting, and accounting systems may reduce errors, improve inventory control and automate record keeping.
For surgical suites and for the purposes of counting surgical items, the medical community has rejected first generation inventory devices, such as bar coding and RFID techniques, because of a perception that the solutions have not been adapted to meet the stringent requirements of the surgical environment. Contrary to popular understanding, however, the RFID tags including tags employing surface acoustical wave technologies may not suffer from many of the perceived limitations. Moreover, the problems which hinder the use of bar coding in the surgical environment do not have the same implications for RFID tags.
As previously mentioned, familiar applications for RFID techniques include “smart labels” in airline baggage tracking and in many stores for inventory control and for theft deterrence. In some cases, the smart labels may combine both RFID and bar coding techniques. The tags may include batteries and typically only function as read only devices or as read/write devices. Less familiar applications for RFID techniques include the inclusion of RFID tags in automobile key fobs as anti-theft devices, identification badges for employees, and RFID tags incorporated into a wrist band as an accurate and secure method of identifying and tracking prison inmates and patrons at entertainment and recreation facilities. Within the medical field, RFID tags have been proposed for tracking patients and patient files, employee identification badges, identification of blood bags, and process management within the factories of manufacturers making products for medical practice.
Typically, RFID tags without batteries (i.e., passive devices) are smaller, lighter and less expensive than those that are active devices. The passive RFID tags are typically maintenance free and can last for long periods of time. The passive RFID tags are relatively inexpensive, generally as small as an inch in length, and about an eighth of an inch in diameter when encapsulated in hermetic glass cylinders. Recent developments indicate that they will soon be even smaller. The RFID tags can be encoded with 64 or more bits of data that represent a large number of unique identification (ID) numbers (e.g., about 18,446,744,073,709,551,616 unique ID numbers). Obviously, this number of encoded data provides more than enough unique codes to identify every item used in a surgical procedure or in other environments that may benefit from asset tracking.
An important attribute of RFID interrogation systems is that a number of tags can be interrogated simultaneously stemming from the signal processing associated with the techniques of impressing the identification information on the carrier signal. A related and desirable attribute is that there is not typically a minimum separation required between the tags. Using an anti-collision algorithm, multiple tags may be readily identifiable and, even at an extreme reading range, only minimal separation (e.g., five centimeters or less) to prevent mutual de-tuning is generally necessary. Most other identification systems, such as systems employing bar codes, usually impose that each device be interrogated separately. The ability to interrogate a plurality of closely spaced tags simultaneously is desirable for applications requiring rapid interrogation of a large number of items.
In addition to tracking and accounting for surgical items, a significant requirement for the management of surgical items involves sterilization procedures and processes. One presently employed sterilization process includes the use of ethylene oxide gas in combination with other gasses at up to three atmospheres of pressure in a special shatterproof sterilization chamber. To achieve effective asepsis levels, this process demands an exposure of the materials to the gas for one or more hours followed by a twelve hour aeration period. The initial gas exposure time is relatively long because the sterilization is effected by an alkylation of amino groups in the proteinaceous structure of any microorganism. Thus, the aforementioned sterilization procedure involves extended exposure of the item to be sterilized to a reactive atmosphere.
A number of other approaches for performing sterilization have also been employed. One such process is high-pressure steam autoclaving. This process exposes the item to be sterilized to high temperatures and is not suitable for materials which are affected by either moisture or high temperature such as corrodible and sharp-edged metals, plastic-made devices or other devices that may be employed in the medical environment. Other sterilization techniques employ x-ray or radioactive sources. While the x-ray procedure is difficult and expensive, the use of a radioactive source requires expensive waste disposal procedures, as well as radiation safety precautions. The radiation techniques also present problems because of radiation-induced molecular changes of some materials which, for example, may render flexible materials such as catheters or bar coded labels brittle.
Other sterilization approaches have been proposed including surface treatment achieved by exposing the medical devices and materials to a highly reducing gas plasma like that generated by gas discharging molecular hydrogen, or to a highly oxidizing gas plasma such as one containing oxygen. Depending on the specific sterilization requirements, a mildly oxidizing environment, somewhere between the environment offered by oxygen and that offered by hydrogen, is presented by gas discharging molecular nitrogen, either in a pure state, or in multi-component mixtures with hydrogen or oxygen, supplemented by an inert gas. In such a manner, plasma discharge chemical-physical parameters can be adjusted to fit almost any practical application of sterilization and surface treatment.
While there are a number of other approaches for performing sterilization, the aforementioned discussion demonstrates that a wide range of thermal, chemical, radioactive and other methods are being employed and further investigated. Very few identification techniques, labeling techniques or marking techniques are compatible with such a wide range of demanding conditions. While a stainless steel instrument may be engraved with a form of a readable tag, such techniques are probably not compatible with disposable items such as sponges.
As alluded to above, RFID tags have been compatible with a number of arduous environments. In the pharmaceutical industry, for instance, RFID tags have survived manufacturing processes that require products to be sterilized for a period of time over 120 degrees Celsius. Products are autoclaved while mounted on steel racks tagged with a RFID tag such that a rack ID number and time/date stamp can be automatically collected at the beginning and end of the process as the rack travels through the autoclave on a conveyor. The RFID tags can be specified to withstand more than 1000 hours at temperatures above 120 degrees Celsius. This is just one example of how RFID tags can withstand the arduous environment including the high temperatures associated with the autoclave procedure, whereas a bar code label is unlikely to survive such treatment.
Returning to the medical environment, on Apr. 4, 2002, Applied Digital Solutions, Inc. announced that it received written guidance that the U.S. Food and Drug Administration (FDA) does not consider its RFID product, VeriChip, to be a regulated medical device. The device has been described in the context of a solution for identifying implanted devices such as pacemakers. Other examples of RFID tags withstanding demanding environments can be seen in the use of such devices for veterinary and animal husbandry purposes. The RFID tags are used to identify millions of livestock animals and pets around the world. The systems track meat and dairy animals, valuable breeding stock and laboratory animals. The tags are typically hermetically sealed and operate over the life of the animal. Body fluids, temperature, mechanical shock, normal electromagnetic interference and radiation such as x-rays do not affect the programmed code within the tag. The tags will not only survive, but will operate reliably in such environments.
While identification tags or labels may be able to survive the difficult conditions associated with medical applications, there is yet another challenge directed to attaching an identification element to a surgical item. The RFID tags are frequently attached to devices by employing mechanical techniques or may be affixed with sewing techniques. A more common form of attachment of a RFID tag to a device is by bonding techniques including encapsulation or adhesion.
While medical device manufacturers have multiple options for bonding, critical disparities between materials may exist in areas such as biocompatibility, bond strength, curing characteristics, flexibility and gap-filling capabilities. A number of bonding materials are used in the assembly and fabrication of both disposable and reusable medical devices, many of which are certified to United States Pharmacopeia Class VI requirements. These products include epoxies, silicones, ultraviolet curables, cyanoacrylates, and special acrylic polymer formulations.
In many instances, the toughness and versatile properties of biocompatible epoxies make them an attractive alternative. Epoxies form strong and durable bonds, fill gaps effectively and adhere well to most types of substrates. Common uses for medical epoxies include a number of applications which require sterilization compatibility such as bonding lenses in endoscopes, attaching plastic tips to tubing in disposable catheters, coating implantable prosthetic devices, bonding balloons to catheters for balloon angioplasty, and bonding diamond scalpel blades for coronary bypass surgery, to name a few. A wide range of such materials are available and some provide high strength bonds which are tough, water resistant, low in outgassing, and dimensionally stable over a temperature range of up to 600 degrees Fahrenheit. Some epoxies can withstand repeated sterilization such as autoclaving, radiation, ethylene oxide and cold (e.g., chemical) sterilization methods.
Regarding the counting of surgical items, a variety of holders are presently available for surgical instruments and disposables items. In many cases, the methods for holding the medical items in a manner that is desirable for transport or for sterilization are combined with configurations for displaying the surgical items in such a way that visual counting can be performed. For instance, U.S. Pat. No. 3,802,555, entitled “Surgical Instrument Package and Handling Procedure,” to Grasty, et al., discloses a surgical instrument package and handling procedure including a set of trays having recessed compartments for surgical instruments. Grasty, et al. and many other references teach that counting procedures are performed visually and there is little flexibility in tailoring the type and number of instruments for different procedures.
Recently, computerized devices have been employed to automatically count the instruments. The computerized devices, however, are relatively complex and expensive such as the surgical count stand described in U.S. Pat. No. 4,943,939, entitled “Surgical Instrument Accounting Apparatus and Method,” to Hoover. To date, these computerized devices require that the surgical instruments and disposable items be placed in a certain location so that a sensor or vision system can detect the presence or, in some cases, the removal of the instrument. These systems suffer from a number of common shortcomings. For instance, the currently available systems do not disclose an apparatus that automatically counts all types of surgical items, and the systems do not eliminate the time, financial costs, and risk associated with counting and recounting the surgical items to verify the specific identity and location of a missing item.
Accordingly, what is needed in the art is an interrogator, interrogation system and related method to identify and account for all types of items such as surgical items in a medical environment that overcomes the deficiencies of the prior art.